Sheshroodbar F(Pb-Zn-Ba) deposit is one of the Mid-Triassic stratabound- stratiform ore deposits of Central Alborz, the oldest outcrop in the area, is the upper part of Elika Fm. (Middle Triassic), which is overlain by Upper Triassic (Paland Fm.), Liassic (Shemshak Fm.) and Malm (Lar Fm.).
  Uppermost part of Elika Fm. is the country rock of the ore bearing horizons, with approximately 207 m. thickness. Elika Fm. consists of silisic limestones, dolomitic limestones and dolomites, in some places with lenses of gypsum, which are faulty placed aside by Shemshak Fm. in the study area.
   Fluorite occurs in 4 horizons, of which 2 main horizons (3rd and 4th) are presently being mined. Geometry of the fluorite horizons are mainly lenticular, and layered, with some congruent breccia lenses. Disseminated, banded and open space filling textures occur in the lower horizons (1 and 2). In the upper horizons, which are under exploitation, the ore textures are disseminated, open space fillings, DCRs, geods, banded, massive, replacement and cement of breccias. The mineral paragenesis consists mainly of fluorite, barite, calcite, galena, sphalerite, quartz and some secondary minerals.
   Based on facies analysis and texture studies, the depositional environment of all facies of upper part of Elika Fm. can be divided into two groups:
1- Relatively quiet environment (without volcanic and tectonic activities)
2- Active environment (with emphasis on the extent of relative intra-basin tectonic and volcanic activities contemporaneous with sedimentation).
     The most important controlling factor of the formation and concentration of fluorite are the manifestation of fumarols and the presence of fluorine, together with contemporary volcanism. In addition, the depositional environment (tidal flat and lagoonal) can also be regarded as another important controlling factor. Facies analysis indicates a shallow environment, involving supratidal, intertidal, shallow subtidal and lagoonal basins.
    On the evidence of high content of authigenic quartz in country rocks, presence of tuff and some pyroclastic fragments in the ore bearing horizon, presence of intraformational breccia and sudden and lateral facies changes, we suggest that the environment of fluorite formation in the Sheshroodbar basin was active.